An Engineering & Electrical Challenge

[stats007]

There are some very intelligent people lurking on this forum (no not you, Howard ) so have theoretical challenge:

1. How easy would it be to create a variable flow-rate in an air-to-water charge cooler?
2. Is it actually worth it?

As far as I'm aware the pump for the charge cooler maintains a constant flow . The heat exchanger obviously likes a high flow but the radiator doesn't. Given that the air volume through the rad increases with speed - should the flow-rate vary accordingly? Obviously air is denser when cool, but how much difference would a reduction in temperature really make - and what is realistically achievable over the standard setup? If inlet temperature drops by 10°C then density increases roughly by 5% (based on 10psi) - how does this translate to power gained?

It seems pretty straightforward - supply vehicle speed or mass air flow and alter the pump voltage based on a map. Alternatively an adaptive system that measures rate of change in inlet air temperature and learns what effect altering the pump voltage has. How do you go from a laptop with software to do this (which I can do) to a microchip in a box (which I can't)?

Is this a waste of time?

 

[Howard]

Oh , that's nice

I'm clever in my own little way , you guys come down and try and control the water flow through SW London , in the middle of the night in the snow ....

 

[stats007]

Wouldn't it be ice instead of water then?

 

[lynall]

Just fit a belt driven pump higher revs equals higher flow.

Or link it to throttle pedal output from the potentiometer.

Must come a point where the higher flow makes no difference and cavitation could be a problem and maybe even pressure.



Lynall

 

[rf065]

As it is theoretical, have you considered fitting an air to air intercooler instead?

Russ

 

[grober]

The problem with an intercooler using engine coolant as the medium for heat transfer is that the difference between the charge air temperature and coolant will be less than in an air to air cooler. Unless you have an abundant supply of "cool water" as in a marine engine installation then you are going to be struggling. Increasing the flow of the coolant wont help much I don't think because the rate of heat exchange will mainly depend on the difference in temperatures of the two fluids. The main problem with heat exchangers is the drop in charge pressure which has to be weighed against temperature drop/density increase. Pointless to drop the temperature if you lose half the pressure in the process. As a Rule of Thumb a 1 degree fall in inlet temperature results in a 1 degree fall in exhaust temperature. If you can lower the charge temperature by 60c then this would reduce the exhaust gas by a similar amount reducing the strain on the exhaust valves. I get the impression that most intercoolers are designed to decrease the thermal loading on the engine rather than increase power for a given boost pressure.

 

[KillerHERTZ]

I'm clever in my own little way , you guys come down and try and control the water flow through SW London , in the middle of the night in the snow ....

"Press the ANY KEY"

 

[lynall]

Grober not having seen one in the flesh i would hazard a guess and say it does not use engine coolant but its own dedicated coolant supply.

Might be worth measuring the temp of the coolant into and out of the intercooler itself.



Lynall

 

[grober]

Good point we are talking general cases when we probably need to be considering a specific set up? As usual in this type of thing the design turns out to be a compromise between size and cost etc etc.

 

[bolide]

I'd have a look at what BBR do when they modify these cars

http://www.morego.co.uk/bbr-gti/home.php

Nick Froome
www.w124.co.uk

 

[stats007]

The car has already been modified by BBR, and yes it has it's own coolant for the charge cooler.

As mentioned you can't just increase flow as the radiator doesn't have time to cool the coolant properly. The flow needs to decrease at certain times to be optimal.

 

[lynall]

So a larger coolant radiator would be the cheapest answer giving the cooler water more time to cool down across the larger surface area?

Or how about a larger coolant reservior assuming it has one, which i guess would act just like a larger rad ie as a heat soak.



Lynall

 

[stats007]

A larger radiator is an option - but I'm still interested in the method of creating an IC.

 

[Dieselman]

You could use some thermistors in the air tract to compare the post cooled temperature and use a comparator circuit to increase flow as it increased.
There will be a maximum heat loss the cooler can dissipate which will be the limit of cooling for that size radiator.
It may be that the water side has a large enough heat sink to be able to cover the maximum requirement given that it's unlikely to be sustained.

For sustained boost conditions an air to air exchanger is better.

 

[stats007]

The car already has an air temp sensor after the throttlebody and idle control valve so could just use that. The real challenge (if accepted it's worthwhile) is to create a module that can alter the pump voltage based on this.

 

[Dieselman]

Shouldn't be too difficult to obtain a motor controller that works of an input voltage. The temp sensor is probably an inverse one so the resistance/feedback voltage reduces as temperature rises.
Feed that through a variable output circuit and you have the controller. The maximum limit of flow can be set by restricting the maximum voltage or pump spec.

 

[Satch]

Suspect you might have limited scope there in terms of added complexity versus the actual gain. Perhaps easier option is just to fit a higher capacity charge cooler rig.

Pretty sure 1200bhp rated kit would do the job!

http://www.thor-racing.co.uk/Charge_Coolers-291.asp

 

[lynall]

8" dia and 22" long wont fit under the bonnet!



Lynall

 

[stats007]

Has anyone any experience of writing their own controllers?

 

[lynall]

Electric water pump controller see here http://www.daviescraig.com.au/main/display.asp?pid=56



Lynall